Development of the inner ear will be studied with light and electron microscopy aided by histochemistry and will be correlated with physiological observations. Further information will be sought about the development of the stria vascularis. The origin of the cells of the deeper layers of the stria and the way some become pigmented will be investigated. The nature of peculiar granulated cells that are evident only during certain stages of development will be studied with the aid of histochemical tests for glycogen. Electrolyte content and resting potential of endolymph will be correlated with morphological maturation of the stria. Innervation patterns of the developing organ of Corti will be investigated with improved techniques for fixation. Cultured otocysts will be subjected to altered media and the effects will be studied by electron microscopy.